Fan controls don't measure up

The fan controls at an airport terminal had never been reviewed, and needed to be updated with variable frequency drives.

Terrence Malloy PE, CxA, exp US Services Inc., Chicago

12/27/2013

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During a recent inspection of the HVAC systems for a 1-million-sq-ft airport terminal, the exp U.S. Services team noticed the installation of inlet vanes on about 35 of the variable air volume (VAV) air handlers. This seemed particularly odd because the fans were only about 10 years old.

When the engineering team inquired about the installation, the client indicated it was a cost issue and that at the installation time the inlet vanes were a cheaper control method than variable frequency drives (VFDs). It seems that a proper design review by the CxA would have addressed this issue, and perhaps suggested a lifecycle cost analysis (LCCA) to show the actual operating costs of using the inlet vane controls versus VFD controls.

The recommendation: replace the inlet vanes with VFDs. Although a moderately costly option, the annual savings are 2,360,000 kWh and $127,000. As a bonus, the state is offering incentives of about $160,000, so the effective payback is around 3.7 years.

Terrence Malloy is project manager for the energy solutions group at exp US Services Inc. He focuses on energy conservation, retro-commissioning, and renewable energy systems.

I fully agree with the VFD analysis and would add that when using a VFD, if you remove the IGVs then the fan energy efficiency will improve about the same as the drive insertion losses. Win-win for both sides!

SIVA , AL, India, 02/02/14 02:20 AM:

vfd is the best and now the only option for a client to get best results in most economical way.only thing consider the duct size